The U.S. trade gap narrowed by $2.3 billion in September, to $41.5 billion, the Commerce Department said Thursday. Oil accounted for more than three quarters of the change, with a $2.2 billion surge in oil exports easily offsetting a small increase in imports.

The one-month change doesn’t mean much — the deficit could widen again when October figures are released next month. But the longer-run trend is unmistakable: The U.S. is importing less oil and exporting more.

The U.S. spent $32.8 billion on oil imports in September and sold $11.2 billion in oil — virtually all of it in the form of gasoline, diesel and other so-called petroleum products — to customers in other countries, for a trade deficit of $21.7 billion. A year ago, that deficit stood at $26.3 billion. Adjusting for inflation, the deficit has shrunk by nearly 40% over the past five years.